Olefin copolymers containing cyclopropane rings in the main chain

ABSTRACT

The invention relates to copolymers of alkenes and conjugated dienes containing cyclopropane and cyclopentane rings in the main chain. These copolymers are charachterised in that the amount of cyclopropane units is between 0.1% and 50% by weight and that the molar percent of the cyclopropane units is higher than the molar percent of the unsubstituted cyclopentane units.

[0001] The invention relates to copolymers based on alkenes andconjugated dienes, which contain cyclopropane and cyclopentane, rings inthe main chain.

PRIOR ART

[0002] It is well known that, among the polymeric materials, polyolefinspresent a high technological relevance. In fact, olefinic homopolymersand copolymers, mainly low and high-density polyethylenes, isotacticpolypropylene, ethylene-propylene and ethylene-propylene-diene rubber,represent nearly 40% of the world market of synthetic polymericmaterials.

[0003] One of the advantages of polyolefin materials is their poorchemical reactivity. In fact, beyond possible functional terminalgroups, which for high molecular mass polymers are present in negligibleamount, chemically reactive group are not present. However, for severalapplications it is important to insert on the polyolefin chains acontrolled number of reactive functional groups, aimed to improve someproperties, like for instance, the adhesion and the compatibility withother materials or aimed to facilitate printing processes on theirsurfaces or to favour their crosslinking processes. It is worth notingthat the introduction of a controlled number of reactive functionalgroups can also allow a control of degradation processes, i.e. of thereduction of molecular mass by aging.

[0004] Only in few cases it is possible to insert reactive functionalgroups in polyolefin chains by copolymerisation processes withfunctionalised monomers, since, in general, the required functionalgroups may not be compatible with the industrially used polymerisationcatalytic systems. As a consequence, the fictionalisation of polyolefinsis mainly obtained by the addition to preformed polyolefin chains offunctionalised organic compounds, mainly by means of radical initiatorsin industrial blenders.

[0005] The European Patent EP-0275 676 discloses ethylene basedcopolymers which include, in their main chain, unsubstitutedcyclopentane rings connected in positions 1 and 2 which can be obtainedthrough ethylene and butadiene copolymerisation, with suitable catalyticsystems. However, due to their high thermodynamic stability, such ringsincluding five carbon atoms cannot be considered reactive functionalgroups.

[0006] The U.S. Pat. No. 6,310,164 discloses unsaturated olefincopolymers based on α olefins and dienes and a process for theirpreparation. The thus obtained copolymers contain in the main chaincyclopentane and cyclopropane units and a high degree of instaurationdue to 1,4 insertion of the diene monomer into the chain. Also in thiscase, the cyclic units are essentially represented by stable five-memberrings, while the more reactive cyclopropane units are present in anegligible molar amount, which is not sufficient to give the neededreactivity to the polymer.

[0007] Scope of the present invention is to provide olefin basedpolymers having high amounts of reactive cyclopropane rings in the mainchain, and, accordingly, being characterized by a higher reactivity withrespect to the polymers of the prior art.

SUMMARY OF THE INVENTION

[0008] The present invention is based on the discovery that reactiveolefin based copolymers can be obtained by copolymerisation reaction ofolefin and diene monomers operating at controlled conditions as totemperature, times and molar ratios between monomers. In particular,copolymerisation reactions conducted by suitable catalytic systemsproduce copolymers containing in the main chain cyclopropane reactiveunits in molar percent markedly higher than that of unsubstitutedcyclopentane units, and also higher than the instaurations along themain chain, due to 1,4 insertion of the diene monomer. Such cyclopropaneunits can possibly be functionalised by opening their cyclic structureby suitable reactants.

[0009] Hence, object of the invention are olefin copolymers based on analkene having 2 to 12 carbon atoms, and a conjugated diene having 4 to 8carbon atoms, which copolymers comprise in the main chain cycloalkaneunits with 3 or 5 members, more precisely cyclopropane units andsubstituted or unsubstituted cyclopentane units. These copolymers arecharacterized by the fact that the amount of cyclopropane units isbetween 0.1% and 50% by weight and that the molar percent ofcyclopropane units is higher than the molar percent of the unsubstitutedcyclopentane units.

[0010] Advantageously the olefin monomer comprises ethylene andoptionally one or more additional olefins, like for instance propylene,while the diene monomer is preferably butadiene.

[0011] When the alkene monomer is propylene and the diene monomer isbutadiene, the cyclic units with five members are3-methyl-1,2-cyclopentane units.

[0012] Further object of the invention are functionalised copolymersobtainable by opening of cyclopropane units through acetylation,hydrohalogenation and esterification reactions.

[0013] Further object of the invention are copolymers, in which thealkene is propylene, the alkyl,1,3,diene is butadiene and the fivemembers cyclopentane units are 3-methyl-1,2-cyclopentane units.

[0014] Further object of the invention are processes for producing thetitle copolymers in which the polymerisation reaction of the mixture ofalkene and conjugated diene monomers is conducted in the presence ofinsertion polymerisation catalytic systems, comprising ansa-metallocenesin which the n ligand is constituted by two bridge-bondedcyclopentadienyl groups, both groups being substituted in positions 3and 4. The catalytic system also comprises a cocatalyst selected fromthe class consisting of linear or cyclic alumoxanes and compoundscapable of forming an alkyl metallocene cation.

[0015] Further object of the invention are preparation processes, whichcomprise as an intermediate step the opening of cyclopropane units byusing suitable reactants.

[0016] Further objects of the invention are articles which comprise, orare prepared with, the copolymers or the functionalised copolymers ofthe invention, optionally blended with other polymeric materials, andprocesses for their preparation, in which the reaction mixture ispolymerised in a defined shape or the polymer melt is shaped or mouldedin a defined shape.

[0017] The use of the copolymers of the present invention in thepreparation of the above cited articles offers several advantages, suchas a better adhesion and compatibility with other polymeric and nonpolymeric materials; moreover, it facilitates printing processes ontheir surfaces and it favours crosslinking processes between linearpolymeric chains.

[0018] Due to these properties, the polymers of the present inventionhave a broad applicability in several technology fields. A specificexample is given by their use, alone or in mixture with other polymers,in the preparation of protective sheaths of electrical materials andcables. Finally, the introduction of a controlled number of reactivefunctional groups allows the control of degradation processes, that isthe reduction of molecular mass with aging, property, which makes thecopolymers of the present invention also suitable for applications inbioadsorbable prostheses or for the degradation of such materials usedfor disposable applications.

DESCRIPTION OF THE FIGURES

[0019]FIG. 1 describes three ¹³C NMR spectra of the copolymers of theinvention.

[0020] Panel 1a represents the spectrum of the copolymer according toExample 1. In particular, it is apparent at least one of the tworesonances, which can be attributed to the methylene group of thecyclopropane ring with trans or cis configurations, localized at 10.1and 9.2 ppm, respectively, as well as at least one of the tworesonances, which can be attributed to the methyne group of thecyclopropane ring with trans or cis configurations, localized at 17.1and 14.1 ppm, respectively.

[0021] Panels 1b and 1c show the spectra of the copolymers according toexamples 2 and 3.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention refers to new olefin based copolymers,which present in the main chain cyclopropane rings of formula (I):

[0023] which, due to their well known thermodynamic instability, can beconsidered reactive functional groups.

[0024] The copolymers of the present invention are copolymerisationproducts of one or more olefin monomers, specifically α olefins having 2to 12 carbon atoms and of a conjugated diene having 4 to 12 carbonatoms.

[0025] In the preferred embodiments of the invention, the olefinmonomers consist of ethylene, propylene or mixtures thereof. The dienemonomer is preferably 1,3-butadiene.

[0026] In the copolymerisation process, the diene molecules can beinserted into the polymeric chain through 1,2 insertion or through 1,4insertion. In the first case, the diene insertion will produceunsaturated branches on the main chain. In the second case, the dieneinsertion will result in instaurations along the main chain.

[0027] Depending on the polymerisation conditions, copolymers ofdifferent compositions which have polymerisation degrees higher than 50,generally with weight average molecular masses in the range 3000-10⁶atomic mass units (a.m.u.), will be obtained.

[0028] The copolymers of the invention contain cyclopropane units offormula (I) in an amount in the range 0.1% to 50% by weight, preferablybetween 1% and 20%, e.g. 10%. Beside to cyclopropane units, thedisclosed copolymers can also contain substituted or unsubstitutedfive-member cyclic units. Provided the latter are unsubstitutedcyclopentane units, their molar amount will be lower than the molaramount of cyclopropane units.

[0029] The copolymers of the invention present ¹³C nuclear magneticresonance spectra comprising at least one of the two resonances, whichcan be attributed to the methylene group of the cyclopropane ring withtrans or cis configurations, localized, respectively, at 10.1 and 9.2ppm (FIG. 1a), as well as at least one of the two resonances, which canbe attributed to the methyne group of the cyclopropane ring with transor cis configurations, localized, respectively, at 17.1 and 14.1 ppm(FIG. 1b). These copolymers can include also close sequences ofcyclopropane rings of the kind:

[0030] which can be detected in ¹³C nuclear magnetic resonance spectraas signals of the main chain methyne and methylene carbons located at15.0 and 38.3 ppm, respectively.

[0031] When the copolymer contains beside cyclopropane units alsosubstituted cyclopentane units, precisely 3-methyl-1,2-cyclopentaneunits, the ¹³C NMR spectrum of the polymer presents resonances at 11.0and 19.9 ppm, which can be attributed to methylene and methyne carbonsof cyclopropane units in trans configuration as well as resonances closeto 15 ppm and 41 ppm which can be attributed to methyl and methynecarbons of 3-methyl-1,2-cyclopentane units.

[0032] The weight fraction of cyclopropane units (X_(Δ)), in ethylenebased polymers can be obtained by the equation:$X_{\Delta} = \frac{{\Sigma \left( {A\quad c_{a}} \right)}40}{\begin{matrix}{{{\Sigma \left\lbrack {\left( {A\quad c_{b}} \right) - {3\left( {A\quad c_{b}} \right)} - {A\quad c_{c}} - {5\left( {A\quad c_{d}} \right)}} \right\rbrack}14} +} \\{{\Sigma \left( {A\quad c_{a}} \right)40} + {{1/2}{\Sigma \left( {A\quad c_{c}} \right)}54} + {{\Sigma \left( {A\quad c_{d}} \right)}68}}\end{matrix}}$

[0033] where: Ac_(a)=area of signals between 9.2 and 10.1 ppm;

[0034] Ac_(b)=area of signals between 5 and 55 ppm, relative to allsaturated carbons;

[0035] Ac_(c)=area of signals between 105 and 150 ppm, relative to thepossible presence of unsaturated carbons;

[0036] Ac_(d)=area of signals close to 22.2 ppm, relative to thepossible presence of cyclopentane rings;

[0037] The molar fraction of cyclopropane units (X_(Δ)), in propylenebased polymers can be obtained by the equation:$X_{\Delta} = \frac{A_{Cb}}{A_{Ca} - A_{Cb} + A_{Cc} + A_{Cd} + {{1/2}A_{Ce}}}$

[0038] where: Ac_(a)=area of signals between 19.0 and 19.9 ppm relativeto methyl carbons of propylene units and to methyne carbons ofcyclopropane units;

[0039] Ac_(b)=area of signals close to 11.0 ppm relative to methylenecarbons of cyclopropane units;

[0040] Ac_(c)=area of signals between 14.9 and 15.5 ppm, relative to themethyl carbons of 3-methyl-1,2-cyclopentane units;

[0041] Ac_(d)=area of signals close to 111 ppm, relative to unsaturatedmethylene carbons of 1,2 inserted butadiene units;

[0042] Ac_(e)=area of signals close to 127.8 ppm, relative to theunsaturated carbons of 1,4 inserted butadiene units.

[0043] The polymers of this invention present a homogeneousintermolecular distribution of cyclopropane rings. The homogeneity ofthis distribution is for instance shown by the fact that the obtainedcopolymers cannot be separated by solvent extraction in significant(larger than 5% by weight) fractions, which present X_(Δ) valuesdiffering more than 50% from the X_(Δ) value of the unfractioned sample.

[0044] To obtain the copolymers described in the present patentapplication it is possible to use homogeneous catalytic systems forinsertion polymerisation of 1-olefins. Ansa-metallocenes based catalyticsystems are preferably used, where the π ligand is constituted by twobridge-bonded cyclopentadienyl groups, both being substituted inpositions 3 and 4. Examples of such metallocenes arerac-methylene-bis-(3-tertbutyl-1-indenyl)ZrCl₂, orrac-isopropylidene-bis-(3-tertbutyl-1-indenyl)ZrCl₂, orrac-dimethylsilyl-bis-(3-tertbutyl-1-indenyl)ZrCl₂, orisopropylidene-bis-(fluorenyl)ZrCl₂, orrac-methylene-bis-(3-isopropyl-1-indenyl)ZrCl₂.

[0045] Since polymerisation yields depend on metallocene purity, thesecan be used, according to the present invention, as such or arepreferably subjected to preliminary purification processes.

[0046] The catalytic system of the present invention also comprises acocatalyst. Suitable cocatalysts are alumoxanes or compounds capable offorming an alkyl metallocene cation. Alumoxanes useful as cocatalystsmay be linear or cyclic. The molar ratio between aluminum and the metalof the metallocene is comprised between about 10:1 and about 5000:1, andpreferably between 100:1 and 4000:1.

[0047] Examples of alumoxanes suitable as cocatalysts in the process ofthe invention are methylalumoxane (MAO), tetra-isobutyl-alumoxane(TIBAO) and tetra-2,4,4-trimethylpentylalumoxane. Further cocatalystssuitable in the catalysts of the invention are those compounds capableof forming an alkylmetallocene cations. Examples are boron compounds,tetrakis-pentafluorophenyl-borate is particularly preferred. Moreover,compounds of formula BAr₃ can be conveniently used.

[0048] The catalysts of the present invention can also be used on aninert support, by depositing the metallocene, or the reaction product ofthe metallocene with the cocatalyst, or the cocatalyst first and thenthe metallocene, on the inert support.

[0049] The metallocene and cocatalyst may suitably be put togetherbefore the polymerisation. The contact time may be comprised between 1and 60 minutes, preferably between 5 and 20 minutes. The pre-contactconcentrations for the metallocene are comprised between 10⁻² and 10⁻⁸mol/l, whereas for the cocatalyst are comprised between 10 and 10⁻³mol/l. The pre-contact is generally carried out in the presence of ahydrocarbon solvent or small amount of monomer.

[0050] The polymer of the present invention can be obtained bycopolymerisation of an olefin of 2 to 12 carbon atoms and of a 1,3diolefin of 4 to 8 carbon atoms. Preferably, the olefin is ethylene,propylene or a mixture thereof, while the diene is 1,3-butadiene. Theolefin concentration is comprised between 0.1 and 7 M, the diolefinconcentration is comprised between 10⁻³ and 9 M, while the metalloceneconcentration is comprised between 10⁻⁸ and 10⁻² M. One or moreadditional olefins, in concentrations comprised between 0.1 and 5 M, canbe advantageously added to the above cited monomers or mixtures ofmonomers. The polymerisation temperature is comprised in the range −30°C.+200° C., preferably between 20° C. and 90° C.

[0051] The molecular mass of the polymers can be varied by changing thepolymerisation temperature or the kind or the concentration of thecatalyst components, or by using molecular mass regulators, such ashydrogen.

[0052] The molecular mass distribution of the polymers can also bevaried by using mixtures of different metallocenes or conducting thepolymerisation in several steps differing for polymerisation temperatureand/or for monomer concentrations.

[0053] The polymerisation process, according to the present invention,can be conducted either in gas or in liquid phase, or in the presence ofan inert hydrocarbon solvent, which may be aromatic, such as benzene ortoluene, or aliphatic, such as hexane, heptane or cyclohexane.

[0054] The polymers object of the present invention can befunctionalised by known reactions suitable for opening three memberhydrocarbon rings, for instance, an acetylation with Pb(Oac)₄, or anhydrohalogenation with HBr, or an esterification with CF₃COOH.

[0055] The invention is further described by the following examples,which however do not limit its scope.

EXAMPLE 1

[0056] In a 100 mL three-neck pyrex glass flask kept at 20° C., 10 mLtoluene and 280 mg methylalumoxane (MAO) are introduced, in thesequence, under nitrogen atmosphere; after nitrogen removal, 2.35 g of1,3-butadiene are dissolved in the liquid phase and, subsequently, 3 mgof the rac-methylene-bis-(3-tertbutyl-1-indenyl)ZrCl₂ catalyst aredissolved, under nitrogen atmosphere, in 2 mL of anhydrous toluene. Thereactor is continuously fed with ethylene by applying an overpressure of3 cm of Hg (with an ethylene concentration of 0.137 mol/L). After a20-hour reaction time, the produced polymer is coagulated in 200 mL ofethanol acidified with HCl, filtered and vacuum dried. The yield isabout 830 mg. The ¹³C NMR spectrum of the polymer (FIG. 1a) presentsresonances at 10.1 and 17.1 ppm, which can be attributed to cyclopropaneunits with trans configuration, and resonances localized at 9.2 and 14.1ppm, which can be attributed to cyclopropane units with cisconfiguration. The ratio between the intensities of the signals relativeto the two configurations is close to 10:1. The analysis of thisspectrum indicates that the polymer is composed by 73 mol % of ethyleneunits, 10 mol % of cyclopropane units, 4 mol % of cyclopentane units, 12mol % of 1,2 inserted butadiene units and 1 mol % of 1,4 insertedbutadiene units (X_(Δ)=0.10).

[0057] From the differential scanning calorimetric analysis, carried outwith a scanning rate of 10 K/min, the polymer results to be essentiallyamorphous.

EXAMPLE 2

[0058] In a 100 mL three-neck pyrex glass flask kept at 20° C., 10 mLtoluene and 280 mg methylalumoxane (MAO) are introduced, in thesequence, under nitrogen atmosphere; after nitrogen removal, 0.40 g of1,3-butadiene are dissolved in the liquid phase, then the internalpressure is increased up to 1.0 atm with ethylene. The reaction isstarted by injecting in the flask, under nitrogen atmosphere, 3 mg ofthe rac-methylene-bis-(3-tertbutyl-1-indenyl)ZrCl₂ catalyst dissolved in2 mL of anhydrous toluene. The reactor is continuously fed with ethyleneby applying an overpressure of 2 cm of Hg. After a 20-hour reactiontime, the produced polymer is coagulated in 200 mL of ethanol acidifiedwith HCl, filtered and vacuum dried. The yield is about 600 mg. The ¹³CNMR spectrum of the polymer (FIG. 1b) presents resonances at 10.1 and17.1 ppm, which can be attributed to cyclopropane units with transconfiguration, and resonances localized at 9.2 and 14.1 ppm, which canbe attributed to cyclopropane units with cis configuration. The ratiobetween the intensities of the signals relative to the twoconfigurations is about 5:1. The analysis of this spectrum indicatesthat the polymer is composed by 95 mol % of ethylene units, 3.8 mol % ofcyclopropane units, 1.2 mol % of cyclopentane units (X_(Δ)=0.038).

[0059] From the differential scanning calorimetric analysis, carried outwith a scanning rate of 10 K/min, the polymer results to becharacterized by a melting temperature of 117° C. (ΔH_(m)=94 J/g)an by aT_(g) inferior to −100° C.

EXAMPLE 3

[0060] The reaction is conducted at 20° C. in an autoclave of 250 mLcontaining 100 mL of toluene, 3.0 g of 1,3-butadiene, 0.29 g ofmethylalumoxane (MAO) and 3 mg of the same catalyst employed in theexamples 1 and 2, by feeding with ethylene at 6 atmospheres. Thereaction is stopped after a reaction time of 2 minutes, and nearly 2.0 gof product are obtained. The ¹³C NMR spectrum of the polymer (FIG. 1c)presents resonances at 10.1 and 17.1 ppm, which can be attributed tocyclopropane units with trans configuration. The analysis of thisspectrum indicates that the polymer is composed by 99.75 mol % ofethylene units, 0.15 mol % of cyclopropane units, 0.1 mol % ofcyclopentane units (X_(Δ)=0.015).

[0061] From the differential scanning calorimetric analysis, carried outwith a scanning rate of 10 K/min, the polymer results to becharacterized by a melting temperature of 130° C. (ΔH_(m)=138.4 J/g) anby a T_(g) inferior to −100° C.

[0062] The homogeneous distribution of comonomers is confirmed byextraction tests with hydrocarbon solvents: the polymer is completelysoluble in boiling hexane and completely insoluble in boilingdiethylether.

EXAMPLE 4

[0063] The reaction is conducted at 50° C. in an autoclave of 250 mLcontaining 100 mL of toluene, 8.1 g of 1,3-butadiene, 0.29 g ofmethylalumoxane (MAO) and 3 mg of the same catalyst employed in theexamples 1, 2 and 3, by feeding with ethylene at 6 atmospheres.

[0064] The reaction is stopped after a reaction time of 9 minutes, andnearly 2.0 g of product are obtained.

[0065] The ¹³C NMR spectrum of the polymer presents resonances at 10.1and 17.1 ppm, which can be attributed to cyclopropane units with transconfiguration, and resonances localized at 9.2 and 14.1 ppm, which canbe attributed to cyclopropane units with cis configuration. The ratiobetween the intensities of the signals relative to the twoconfigurations is about 8:1. The analysis of this spectrum indicatesthat the polymer is composed by 97.9 mol % of ethylene units, 1.2 mol %of cyclopropane units, 0.9 mol % of cyclopentane units (X_(Δ)=0.012).

[0066] From the differential scanning calorimetric analysis, carried outwith a scanning rate of 10 K/min, the polymer results to becharacterized by a melting temperature of 122° C. (ΔH_(m)=136.5 J/g).

EXAMPLE 5

[0067] In a 100 mL three-neck pyrex glass flask kept at 20° C., 10 mLtoluene and 280 mg methylalumoxane (MAO) are introduced, in thesequence, under nitrogen atmosphere; after nitrogen removal, 0.330 g of1,3-butadiene are dissolved in the liquid phase, then the internalpressure is increased up to 1.0 atm by propylene. The reaction isstarted by injecting in the flask, under nitrogen atmosphere, 3 mg ofthe rac-methylene-bis-(3-tertbutyl-1-indenyl)ZrCl₂ catalyst dissolved in2 mL of anhydrous toluene. The reactor is continuously fed withpropylene by applying an overpressure of 20 cm of Hg.

[0068] After a 15-hour reaction time, the produced polymer is coagulatedin 200 mL of ethanol acidified with HCl, filtered and vacuum dried.

[0069] The yield is about 300 mg. The ¹³C NMR spectrum of the polymerpresents resonances at 11.0 and 19.9 ppm, which can be attributed tomethylene and methyne carbons of cyclopropane units in transconfiguration as well as resonances close to 15 ppm and 41 ppm which canbe attributed to methyl and methyne carbons of 3-methyl-1,2-cyclopentaneunits. The analysis of this spectrum indicates that the polymer iscomposed by 88.8 mol % of ethylene units, 1 mol % of cyclopropane units(X_(Δ)=0.01), 3.2 mol % of 3-methyl-1,2-cyclopentane units, 2.5 mol % of1,2 inserted butadiene units and 4.5 mol % of 1,4 inserted butadieneunits.

1. Olefin copolymers of an alkene having 2 to 12 carbon atoms and of aconjugated diene having 4 to 8 carbon atoms, which comprise in the mainchain cyclopropane units and substituted or unsubstituted cyclopentaneunits, characterized in that the amount of cyclopropane units is between0.1% and 50% by weight and that the molar percent of cyclopropane unitsis higher than the molar percent of the unsubstituted cyclopentaneunits.
 2. The copolymers according to claim 1 wherein the alkene isethylene and/or propylene and the conjugated diene is butadiene.
 3. Thecopolymers according to claim 1 wherein the alkene is propylene, theconjugated diene is butadiene and the cyclopentane units are3-methyl-1,2-cyclopentane units.
 4. The copolymers according to claim 1which present a degree of polymerisation not lower than
 50. 5. Processfor the production of olefin copolymers of an alkene having 2 to 12carbon atoms and of a conjugated diene having 4 to 8 carbon atoms, whichcomprise in the main chain cyclopropane units and substituted orunsubstituted cyclopentane units and in which the amount of cyclopropaneunits is between 0.1% and 50% by weight and the molar percent ofcyclopropane units is higher than the molar percent of the unsubstitutedcyclopentane units, characterized in that the polymerisation reaction ofthe alkene and conjugated diene mixture is conducted in the presence ofinsertion polymerisation catalytic systems.
 6. Process according toclaim 5, wherein the olefin monomer is ethylene and/or propylene and theconjugated diene is butadiene.
 7. Process according to claim 5, whereinthe catalytic system comprises ansa-metallocenes in which the π ligandis constituted by two bridge-bonded cyclopentadienyl groups, both beingsubstituted in positions 3 and
 4. 8. Process according to claim 5,wherein the catalytic system comprises ansa-metallocenes in which the πligand is constituted by two bridge-bonded cyclopentadienyl groups, bothbeing substituted in positions 3 and 4 and a cocatalyst selected fromthe group consisting of linear or cyclic alumoxanes and compoundscapable of forming an alkyl metallocene cation.
 9. Process according toclaim 8, wherein the cocatalyst is an alumoxane and the molar ratiobetween aluminum and the metal of the metallocene is comprised between10:1 and 5000:1, and preferably between 100:1 and 4000:1.
 10. Processaccording to claim 5, wherein the reaction is conducted at a temperaturecomprised between −30° C. +200° C., preferably between 20° C. and 90°C., and wherein the olefin monomer concentration is comprised between0.1 and 7 M, the diene monomer concentration is comprised between 10⁻³and 9 M, and the catalyst concentration is comprised between 10⁻⁸ and10⁻² M.
 11. Process according to claim 5, wherein the reaction mixturefurther comprises one or more additional olefins in concentrationbetween 0.1 and 5 M.
 12. Functionalised copolymers obtainable from thecopolymers according to claim
 1. 13. Functionalised copolymers,obtainable from the copolymers according to claim 1 by opening thecyclopropane units through acetylation, hydrohalogenation oresterification reactions.
 14. Process for the preparation offunctionalised copolymers according to claim 12, which comprises openingthe cyclopropane units with suitable reactants.
 15. Articles comprisingor realized with the copolymers according to claim 1, optionally blendedwith other polymeric materials.
 16. Article comprising or realized withthe functionalised copolymers according to claim 12 optionally blendedwith other polymeric materials.
 17. Article, according to claim 15, inthe form of sheath for electrical cables.
 18. Article, according toclaim 16, in the form of sheath for electrical cables.
 19. Article,according to claim 15, obtained through crosslinking process. 20.Article, according to claim 16, obtained through crosslinking process.21. Process for the manufacture of articles comprising or realized withthe copolymer according to claim 1, or with a functionalised copolymerthereof, wherein said copolymer according to claim 1 or saidfunctionalised copolymer thereof, optionally in the presence of othermaterials, is polymerised in a defined shape or the polymer melt isshaped or moulded in a defined shape.
 22. A process for the preparationof copolymers according to claim 1 wherein a catalytic system comprisinga catalyst selected from rac-methylene-bis-(3-tertbutyl-1-indenyl)ZrCl₂,or rac-isopropylidene-bis-(3-tertbutyl-1-indenyl)ZrCl₂, orrac-dimethylsilyl-bis-(3-tertbutyl-1-indenyl)ZrCl₂, orrac-isopropylidene-bis-(fluorenyl)ZrCl₂, orrac-methylene-bis-(3-isopropyl-1-indenyl)ZrCl₂ and a cocatalyst selectedfrom methylalumoxane (MAO), tetra-isobutyl-alumoxane andtetra-2,4,4-trimethylpentylalumoxane or compounds capable of forming analkylmetallocene cation is used.
 23. The process, according to claim 22,wherein the catalytic system is in form of solution or is deposited ontoan inert support.